The present invention relates to a microprocessor based apparatus for use in producing perforated pounce patterns in sheet material for use in painting signs and the like, and deals more particularly with such an apparatus for forming improved perforations in the sheet material.
Apparatus for pouncing or perforating sheet materials to form perforated patterns in the shape of sign characters are known in the art. Pouncing is sometimes employed by signmakers for dusting the outline of letters or other characters onto a sign board or other surface to display a sign. The sign surface is covered with an appropriately perforated sheet material overlay and then dabbed with a dusting pad or bag to deposit slight traces of dust through the perforations and onto the surface to form a dusted outline of the sign characters to be displayed. The signmaker then uses the dusted outline as a guide for painting the sign.
U.S. Pat. No. 4,467,525 describes a microprocessor-based apparatus used for pouncing or perforating materials along the profiles of sign characters. In this patent, the apparatus disclosed comprises a rotatable feed and backup roller having a work-engaging surface for both supporting the sheet material and for moving it back and forth. A tool carriage is supported adjacent the feed and backup roller and is moveable in a direction parallel to the roller axis, and a tool receiver is mounted on the tool carriage. This receiver is rotatable in a .theta.-coordinate direction about an axis extending generally radially of the roller axis and is movable generally along such axis in a Z-coordinate direction between elevated and lowered positions relative to the roller. A tool is releasably fixed in the tool receiver and is movable with it.
A pouncing tool may be the one fixed in the tool receiver and includes a pouncing wheel with a plurality of radially extending teeth or punch pins rotatably connected to the lower end of a support member for rotation relative to the support member about the central axis of the wheel. The punch pins are substantially needle-like in shape for perforating the sheet material. A microprocessor based controller controls the positioning of the tool carriage relative to the roller in an X-coordinate direction extending along the length of the roller, the feed of the sheet material in a Y-coordinate direction by rotation of the feed and backup roller, and the movement of the receiver in the .theta. and Z-coordinate directions.
During a perforating operation, the controller is operated to move the tool carriage to a selected position and to move the pouncing tool to a lowered position for placing the punch pins into working engagement with the sheet material supported on the roller. The controller then operates to cause movement of the pouncing tool along one or more lines on the sheet material to form one or more perforated paths conforming to the profiles of selected sign characters.
A problem associated with the use of the above-described apparatus is that the perforations formed by the needle-like punch pins are small and generally circular in shape. As a result, the portions of sheet material pushed away to form the individual perforations tend to move back over and close the perforations prior to or when the pounce pattern is placed over the surface to be painted. Therefore, when the pattern is dusted, the outline formed may be incomplete or indistinct in sections where the perforations become closed or nearly closed. The painter may then use a hand held needle or similar instrument to individually reopen each of the closed perforations and redust the outline on the sign surface to be painted. As a result, the use of a pounce pattern to form a dusted outline may become a tedious process.
It is accordingly an object of the present invention to provide an improved apparatus for producing a pounce pattern that overcomes the drawbacks and disadvantages of known pounce pattern producing apparatus.